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86 Cards in this Set
- Front
- Back
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Organic compounds that are soluble in organic solvents, but insoluble in water
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Lipids
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Lipids are mostly comprised of what?
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C-H bonds
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Under what condition does lipids yeild fatty acids?
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hydrolysis
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Under what condition is an ester formed?
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when complex alcohols combine with fatty acids
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What are the four major functions of lipids?
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1.Critical structural components of biological membranes
2.provide an efficient way for the body to store excess calories 3. provide readily available energy sources 4.serve as essential vitamins and hormones |
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Name the major lipids (6)
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1.fatty acids
2.triglyceride 3.cholesterol 4.cholesteryl esters 5.phospholipids 6.bile acids |
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Linear chains of C-H bonds with COOH at one end.
Mostly unsaturated in nature with even number of carbon atoms |
Fatty acids (R-COOH)
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What is the structure of triglycerides?
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A triglyceride is a triacyl-glycerol. It is composed of a glycerol backbone and 3 fatty acids.
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What is the structure of a phospholipid?
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2 esterfied fatty acids (consisting of 14-24 C) and a phospholipd head group
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a soapy surfactant in amniotic fluid
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Phosphotidal choline
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Cholesterol and closely related cholesteryl esters are considered
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Sterols
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Descride the composition of a cholesterol
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27 C atoms; slightly polar due to free OH at C3
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Describe the composition of a cholesteryl ester
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Cholesterol molecule with fatty acid (or phospholipid) esterfied at C3-OH group
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What are cholesterols broken down into?
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Bile acids
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Describe the composition of Bile acids
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24 Carbons, 24 Carboxyl plus OH groups
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Whats the function of Bile acids
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Promote fat absorption in the intestine by acting as detergents (emulsifiers)
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A lipid with no double bonds, more polarity, and the ability to go through membranes is characteristic of
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Bile acids
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What is the main structural difference between a Bile acid and a cholesterol?
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Bile acids have 2 extra hydroxyls (OH)
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Lipids that bind to protein become more _____. This is because of the ________ groups.
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Polar; carboxyl
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lipoprotein with 84% TG and 1% Chol
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Chylomicrons
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44-60% TG
16-22% Chol |
VLDL
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23% TG
29% Chol 52% Lipid |
IDL
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11% TG
62% Chol 28% lipid |
LDL
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3% TG
19% Chol 78% Lipid |
HDL
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Why are apolipoproteins used?
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In order to be transported in blood, lipids must combine with water soluble compounds.
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This lipoprotein forms as a result of lipolysis of VLDL; It is readily taken up by cells via receptors in the liver & peripheral cells; It is significantly smaller thans VLDLs and can infiltrate extracellular space
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LDL (low density Lipoproteins)
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LDL-like particles; heterogeneous in size & density. Plasma levels vary widely among individuals in population but remain relatively constant within a person.
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Lipoprotein (a), Lp(a)
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People with higher Lp (a) are more at risk for
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Cardiovascular disease
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Smallest & most dense; synthesized by liver & intestine.
Can exist either as disk-shaped or spherical particles Capable of removing excess cholesterol from peripheral cells Highly heterogeneous; can be separated into 13 or 14 subfractions. This is good cholesterol for you. |
High density lipoproteins
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Functions as transport proteins for lipids; made by the liver. Are packaged with VLDL and HDL as they are released from the liver.
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Apoproteins
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Cells containing lipoprotein lipase do what?
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metabolize VLDL, leading to LDL formation, which results in the release of apo C and E, while keeping the apoprotein B-100.
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What happens to the loose apoproteins in LDL formation? (Apo C and E)
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The loose apoprotein can be taken up by circulating HDL particles or they can be degraded into their amino acid constituents.
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Functions of apoproteins (3)
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1. Activates enzymes in lipid metabolism
2. Maintain structural intergrity of lipid/protein complex 3. Delivery of lipids to cells via recognition of cell surface receptors |
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A protein on the surface of a membrane capable of attaching to another protein or enzyme
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receptor
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Four major pathways involved in lipoprotein metabloism
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1. Lipid absorption pathway
2. The exogenous pathway 3. The endogenous pathway 4. Reverse Cholesterol transport pathway |
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What is the reverse cholesterol transport pathway?
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A pathway mediated by HDL to transport cholesterol back to liver for further breakdown
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Cholesteryl ester is hydrolyzed by cholesterol esterase to form?
*the cholosterol esterase is in pancreatic juice* |
free cholesterol and free fatty acid
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What happens to the free cholesterol and free fatty acids formed by cholesteryl ester?
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Half of the cholesterol and fatty acids diffuse through the cell membranes of intestinal cells into lymphatic vessels.
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Triglycerides cannot diffuse through intestinal cell membranes, what must happen to change that?
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It must be hydrolyzed into fatty acids and free glycerol
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A triglyceride coated with a thin skin of phospholipids and apoproteins CII and B48, plus a little E
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Chylomicron
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Explain the role of HDL in the reverse cholesterol Pathway
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HDL contains apoprotein A-1 and cholesterol. Apo A-1 is a cofactor for the enzymatic action of Lecithin cholesterol acyltransferase (LCAT), an enzyme in circulation that esterifies a fatty acid to a cholesterol molecule.
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What is the function of HDL in the reverse cholesterol pathway
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Accepts cholesterol transferred out of cell and delivers it to other cells.
Converts Cholesterol to Cholesterol esters by LCAT for further metabolism |
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The deposition of lipids in various tissues within the body
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atherosclerosis
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what are the cholesterol risk factors in atherosclerosis
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-low HDL <40 mg/dL
-High LDL >100 mg/dL - High total Chol. >200 mg/dL |
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What are the laboratory guidelines for desirable lipid levels
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-Total =/<200 mg/dL
- LDL =/< 100 mg/dL - HDL=/> 60mg/dL |
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What does is mean if chylomicrons are seen in a fasting sample?
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There is a metabolic disorder
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What lipid level is not directly associated with CHD? What is the recommended level?
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Triglycerides; <150 mg/dL
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What lipid level is an independent risk factor for CHD? What is the recommended level?
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Lp(a); <30 mg/dL
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What is the relationship between Lp(a) and plasminogen?
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Lp(a) is structurally similar to plasminogen. Lp(a) competes with plasminogen to clots, and will not allow degrading of the clots by attracting the plasminogen activators to it.
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Pre- menopausal women, persons who excercise regularly, persons who maintain a low but healthy weight is associated with?
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High HDL levels
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What three things have an inverse relationship with total cholesterol levels?
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Insulin, Estrogen, and Thyroxine (T4)
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What are three different types of treatments for cholesterol?
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1.Statin drugs
2. Fibrate drugs 3. Cholestyramine |
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What do statin drugs do?
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Inhibit enzyme HMG-CoA reductase (converts acetyl coA to cholesterol); Increase HDL and reduces LDL
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What do fibrate drugs do?
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Activate LPL and promote rapid VLDL turnover; decreases secretion of VLDL
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What does Cholyestryamine do?
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Bind bile acids which are not reabsorbed by the liver but are excreted; decreases plasma cholesterol
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Primary Hyperlipoproteinemias is characterized by
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Elevations of low density and high density lipoproteins; Hypertriglyceridemia can result from lipoprotein lipase deficiency
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Secondary Hyperlipoproteinemias is characterized by
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diabetes mellitus; blood pressure medication; estrogen horomone replacement therapies; nephrotic syndrome and chronic renal failure; hepatic disorders
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Elevations of low density and high density lipoproteins can rarely result from inborn errors of metabolism such as from enzyme or apoprotein lipase deficiency
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Primary causes of hyperlipoproteinemias
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hyperlipoproteinemias can result in
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hypertriglyceridemia resulting from lipoprotein lipase deficiency
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Secondary problems that can cause secondary hyperlipoproteinemias? (5)
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diabetes mellitus
bloodpressure medication estrogen hormone replacement therapies nephrotic syndrome and chronic renal failure hepatic disorders |
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Two types of hypercholestrolemia are?
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hypercholestrolemia and familial hypercholestrolemia
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most common is high LDL; secondary to diabetes mellitus, some renal diseases etc.
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hypercholestrolemia
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due to deficiency/ defect in LDL receptors--> high LDL and risk for atherosclerosis. premature CHD.
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Familial hypercholesterolemia
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Can synthesize cholesterol efficiently but cannot correctly metabolize it. Treatment is usually statin drugs to stimulate LDL recpetors
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Familial hypercholesterolemia
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what is the result of hypercholesterolemia in a homozygote?
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homozygotes are rare and usually result in a MI in childhood
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what are three types of hypertriglyceridemia?
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familial triglyceridemia, triglyceridemia, and severe hypertriglyceridemia
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this triglyceridemia is genetic
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Familial triglyceridemia
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secondary to hormonal abnormalties or DM
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triglyceridemia
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LpL deficiency or apoprotein CII deficiency
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severe hypertriglyceridemia
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presence of high serum cholesterol and triglyceride
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Combined hyperlipoproteinemia
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two types of combined hyperlipoproteinemias
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Familial combined hyperlipoproteinemia and familial dysbetalipoproteinemia(typeIII)
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due to overproduction of VLDL and B-100-> high trig, low HDL and high risk of CHD
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familial combined huperlipoproteinemia
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high VLDL and chylomicron remnants due to the presence of a rare form of apoE. VLDL equally rich in trig and chol.
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familial dysbetalipoproteinemia (type III)
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decrease in HDL (<40 mg/dL) exhibited from absence or non-detectable levels of apo A-1.
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hypoalphalipoproteinemia
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associated with increased risk of CHD due to plaque build up and blockage of blood vessels from excessive LDL.
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hypoalphalipoproteinemia
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HDL acts like a sink and clears...
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cholesterol
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includes hyperbetalipoprotein or familial defective Apo B-100, where there is an absence of normal apo-protein b-100 due to an amino acid substiution in the B-100 structure
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hyperbetalipoproteinemia
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lack of LDL uptake by steroid generating tissues because of poor receptor specificity; leads to deposition of cholesterol esters in tissues, hepatomegaly, and even loss of eye sight due to clouding of the cornea
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Hyperbetalipoproteinemia
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lapid results show increased LDL and total cholesterol
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hyperbetalipoproteinemia
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What is the sample of choice for lipid analysis? Fasting?
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serum; a minimum twelve hour fast
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In triglyceride analysis what reactions take place?
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detergent breaks up lipoprotein particles into their parts--> releases triglycerides into the solution
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What are problems and pitfalls in triglyceride analysis?
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free glycerol in the sample is measured and calculated as if it were a triglyceride. Standards are glycerol (H2O soluble) insted of triglyceride (insoluble) large error if the detergent step or lipase doesn't work
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Reaction in a cholesterol analysis
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detergent breaks up lipoprotein particles into their parts--> releases cholesterol and cholesterol esters into the solution
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What are the reagents in HDL analysis? What make HDL analysis different from others?
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dextran, or Mg2+; it is different because the reagent dissolves the HDL particles while leaving LDL and VLDL in tact and the dissolved particles are measured.
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What is the freidwald formula?
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total chol= HDL-LDL- VLDL(tri/5)
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When can freidwald formula not be used? what is the significance of the result?
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it is because trig >400; this usually means chylomicrons are present and VLDL is not trig/5
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